The present inventions relate generally to static transfer switches, and more particularly, to turning off the switches therein.
A static transfer switch (STS) is a known type of electrical component that is used to distribute electric power to sensitive loads. For example, static transfer switches are commonly used to supply electric power to data centers or other industrial plants or facilities where constant, reliable power is necessary.
A static transfer switch is used to switch between multiple power sources to supply a load with electric power. For example, one power source, such as an electric grid, may be a primary power source, and a second power source, such as a generator, may be a backup power source. Both power sources are supplied to the static transfer switch which supplies power to the load. During normal conditions, the static transfer switch monitors the primary power source and a backup power source, and supplies power from the primary power source to the load. When the power from the primary power source deteriorates, the static transfer switch switches to the backup power source to supply the load. Such switching is designed to happen quickly enough that the load is not affected by the switch between power supply sources.
In order to achieve the desired switching speed and reliability, static transfer switches use “static” switching, meaning that solid-state power electronics are used to switch between power sources. However, even with the use of solid-state power electronics, switching speed is a concern with static transfer switches. For example, deterioration in the primary power source can happen suddenly, and it is important to switch away from a deteriorating primary power source quickly. That is, many of the electrical components, for example in a data center, are particularly sensitive to power supply fluctuations. Moreover, the timing of the switching between the two power sources must be seamless. Thus, for example, it is undesirable for a delay in disconnecting a power source to result in a spike in power by temporarily having multiple power sources connected to the load or to allow a gap in power by temporarily having no power source connected to the load. Therefore, it is important in a static transfer switch to be able to disconnect a power source as quickly as possible when switching between power sources.